JP4742616B2 - Three-dimensional elliptical optical device - Google Patents

Description

  The present invention incorporates an external light source and detector such as a laser or microwave source into a system or a sample chamber of a dispersive spectrophotometer or a Fourier transform spectrophotometer, so that the reflectivity can be obtained with the same setting of the sample. The present invention relates to an optical system using a bielliptic mirror capable of sequentially measuring transmittance and diffuse reflectance.

  The structure of the bielliptical optical system is described in detail in Japanese Patent Application Laid-Open Nos. 2004-45065 and 2004-257956. FIG. 5 is a perspective view of a planar bielliptic optical system, and FIG. 6 is a cross-sectional view of the equatorial plane of the bielliptic mirror. The structure is such that the incident-side ellipsoidal mirror E1 and the light-receiving ellipsoidal mirror E2 have a common focal point F0 as one focal point and F1 and F2 as the remaining focal points of the E1 mirror and the E2 mirror, respectively. These three focal points are constructed so as to be aligned in a straight line. This straight line is called an optical axis, and a hole is made at the intersection of this optical axis and each E1 mirror and E2 mirror. Then, beam rotating mirrors RM1 and RM2 are attached to the focal points F1 and F2, respectively, and a sample is attached to the common focal point F0. A bielliptic optical system having a structure in which the optical axis of the external light source and detector and the optical axis of the bielliptic mirror are in a straight line is called a planar bielliptical optical system.

  When the light traveling on the optical axis is taken into the double ellipsoidal mirror through one hole (the ellipsoidal mirror having this hole is called the E1 mirror), the light reaches the RM1 mirror. In this double ellipsoidal mirror structure, an arbitrary angle of incidence on the sample can be realized by appropriately rotating the RM1 mirror (see FIG. 6). The light reflected by the appropriately rotated RM1 mirror is further reflected by the E1 mirror and enters the sample on the common focal point. The light reflected by the sample (solid line in FIG. 6) and the light transmitted through the sample (broken line in FIG. 6) are reflected by the E2 mirror and collected at the F2 focal point. By appropriately rotating the RM2 mirror on the F2 focal point, the light incident on the RM2 mirror can be reflected so as to coincide with the original optical axis. Thus, this light can be taken out of the bielliptic mirror through the hole formed in the E2 mirror and guided to a detector or the like.

  FIG. 7 shows the arrangement of optical measurement of reflection, transmission and scattering of a sample using this bielliptic mirror. In this example, a laser is used as a light source. Basically, all optical measurements can be performed at an arbitrary incident angle by simply arranging optical elements in a straight line as in normal transmission measurement.

  When the sample is opaque and the incident surface is a mirror surface, for example, a mirror, the light regularly reflected by the sample is reflected by the E2 mirror and then collected at the focal point F2. This light can be guided outside the bielliptic mirror by appropriately rotating the RM2 mirror on F2. As a result, the light collected at the focal point F2 is not reflected again and returned to the sample.

  Next, in the case where the sample is a transparent sample and the incident surface is a mirror surface, for example, a parallel plate of quartz, the light incident on the sample from the E1 mirror side is reflected by the light L1 (see FIG. (Solid line 6) and light L2 (dotted line in FIG. 6) that has passed through the sample exist inside the E2 mirror, and are both reflected by the E2 mirror and then focused on the focal point F2. At this time, the RM2 mirror can reflect either L1 or L2 so as to coincide with the optical axis, and the light is guided to the outside of the bielliptic mirror through the hole on the E2 mirror and reaches the detector. Either the reflection spectrum or transmission spectrum of the sample can be measured.

JP 2004-45065 A JP 2004-257956 A

  However, when the sample is a transparent sample, the light not measured above is reflected by the side and back of the RM2 mirror and the RM2 mirror holder, and partly reflected again by the E2 mirror, and then returns to the sample. Reflected light and transmitted light are created. In this case, these exist on the E1 mirror side, and are reflected by the E1 mirror, reach the RM1 mirror on the F1 focal point, and part thereof may be reflected again toward the sample side. Such light repeats multiple reflections inside the double ellipsoidal mirror, is called stray light, and appears as noise on the measurement signal.

  An example is shown in FIG. In this measurement, the sample is a parallel plate of high purity quartz having a thickness of 1 mm, and the measurement light is 0.633 μm of a helium neon laser. It is the result of measuring the incident angle dependence of the reflectance when the P-polarized component of this laser beam is obliquely incident on the sample. The white squares in the figure are the measurement results. Black ■ is the result of measurement by the same method when laser light is not incident on this double ellipsoidal mirror, and is the zero signal level of this double ellipsoidal mirror. The minimum reflectance of white square was 0.0012. In a high purity quartz sample, this minimum value should be zero, but remains in a finite value in this way. The reason for this is stray light due to multiple reflection inside the above-mentioned bielliptic mirror.

  Further, when the sample is a diffuse reflector, the stray light becomes a large noise source. The reflection surface of the diffuse reflector is not a mirror surface but a rough surface or a porous surface. Light incident on the sample surface from the E1 mirror side is irregularly reflected on the sample surface, and the reflected light is reflected by the E2 mirror. Reflected not only on the side but also on the E1 mirror side. The light reflected to the E2 mirror is collected at the focal point F2, but only a part of the light is reflected by the RM2 mirror so as to coincide with the original optical axis and guided to the detector outside the bielliptic mirror. The angular dependence of diffuse reflectance can be measured. However, some of the light that was not extracted to the outside by the RM2 mirror and some of the light that was reflected by the E1 mirror and reached the RM1 mirror at the F1 focal point were repeatedly reflected inside the bielliptic mirror and became stray light. , It becomes noise of the measurement signal.

  In a conventional planar elliptical optical system using a double ellipsoidal mirror, a technique for reducing stray light has not been developed. For this reason, it is difficult to measure reflection, transmission and scattering because of stray light.

  An object of the present invention is to provide a bielliptic optical system capable of removing stray light and performing highly accurate measurement.

  In the present invention, as a method for reducing stray light, two methods are used: (1) a method using a light-absorbing substance and (2) a method for excluding unmeasured light to the outside of the bielliptic mirror. Alternatively, these two methods can be used in combination.

That is, stereoscopic twin elliptical optical device according to the invention, the incident-side rotational ellipsoidal mirror whose inner surface has a mirror surface, respectively and the light receiving side spheroidal mirror, the one focus and the common focus, a common focus and the common focus combined as a second focal point of the first focus and the light receiving side rotational ellipsoidal mirror on the incident side rotational ellipsoidal mirror other than are positioned in a straight line on the optical axis, bi-ellipsoidal mirror having an opening provided in the upper and lower And a sample holder for holding the sample at the position of the common focus, and first light for causing the incident light for sample irradiation to enter the first focus from the opening along the first axis perpendicular to the optical axis. And a second reflector disposed at the first focal point and rotatable about the first axis, and a second axis disposed at the second focal point and parallel to the first axis. A third reflecting mirror that is freely rotatable, and a fourth reflector that reflects the light reflected by the third reflecting mirror toward the detector. And a mirror, the second reflecting mirror, bi a first face incident light reflected by the reflecting mirror Ru is incident on a common focus is reflected by the inner surface of the incident-side rotary ellipsoidal mirror, other than the incident light and a surface for reflecting the outside of the ellipsoidal mirror, a third reflecting mirror, is incident measurement light reflected by the inner surface of the light-receiving side spheroidal mirror After interacting with the sample to the fourth reflecting mirror It has a surface and a surface that reflects the measurement light other than the double ellipsoidal mirror . The ellipsoid constituting the ellipsoidal mirror may be a spheroid or an elliptic cylinder.

Side where the measuring light is present to at least a portion and / or the light receiving side spheroidal mirror inside the optical axes of the side on which the incident light exists opposite side of the space with respect to the optical axis of the inner entrance side spheroidal mirror It is preferable to provide a light absorbing member that functions as means for reducing stray light inserted into at least a part of the space on the opposite side of the space.

The second reflecting mirror and / or the third reflecting mirror functioning as a means for reducing stray light is disposed inside a conical member connected to the rotation axis, and the conical member has a mirror surface on the outer surface and is arranged from the top to the inside. And a hole extending from the conical side surface to the reflecting mirror disposed inside. The second reflecting mirror and / or the third reflecting mirror is also disposed inside the conical member connected to the rotation axis, and the conical member has a mirror surface on the outer surface and is disposed from the bottom surface to the inside. And a hole extending from the conical side surface to the reflecting mirror disposed therein. The second reflecting mirror and / or the third reflecting mirror is also disposed inside the member connected to the rotation axis, and the member has an outer surface that is a light absorbing surface and rotates from the inner reflecting mirror to the member side surface. You may have a hole extended in parallel with an axis | shaft, and a hole extended perpendicularly | vertically to a rotating shaft from an internal reflecting mirror to a member side surface.

  The third reflecting mirror includes a conical member connected to the rotation shaft, and the conical member may have a mirror surface on the outer surface and a hole on the side surface for absorbing the specular reflection component from the sample. it can.

  According to the present invention, it is possible to measure the reflection, transmission, or diffuse reflection of a sample with high accuracy without being affected by stray light.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 9 is a schematic diagram showing an embodiment of a planar bielliptical optical system according to the present invention. In this embodiment, in a planar bielliptic optical system, a light absorbing member is arranged in a region where light that is not measured is present inside the bielliptic mirror, and light that is not measured is absorbed by the light absorbing member, so that stray light is absorbed. Reduce. Alternatively, the same effect can be obtained by applying a light absorber to the mirror holder and sample holder of RM1 and RM2. The illustrated example is an example in which the reflection of the sample is measured, and a black felt cloth is inserted as a light absorbing member into the space between the light transmitted from the sample (broken line in FIG. 9) reaching the E2 mirror and transmitted as stray light. The light was absorbed. The black felt cloth is fixed to the support, and is inserted into the inside of the double ellipsoidal mirror through an opening provided below or above the double elliptical mirror. When measuring the transmission spectrum of the sample, the light absorbing member may be inserted into the space while the reflected light from the sample (solid line in FIG. 9) reaches the E2 mirror.

  The experimental results using this light absorbing member are shown in FIG. The result of FIG. 8 is that the light reflected from the quartz parallel plate and reflected to the E2 mirror side is the measurement light, and the light transmitted through the quartz parallel plate and transmitted to the E2 mirror side is stray light. Therefore, the incident angle dependence of the P-polarized reflectance when a black felt cloth is placed and absorbed in a space while the transmitted light from the sample reaches the E2 mirror is indicated by white Δ. In this measurement, the minimum reflectance was 0.0003. In the method using the black felt cloth, the reflectance could be made zero depending on the arrangement. The result of FIG. 8 is an average value of measurement results obtained many times. Thus, the method using the light absorbing member is important as a stray light noise reduction technique of the planar bielliptical optical system.

  FIG. 1 is a diagram showing another embodiment of a bi-elliptical optical device according to the present invention. In this figure, the broken line indicates the progress of light.

  The illustrated bi-elliptical optical device includes an incident-side ellipsoidal mirror E1 and a light-receiving-side ellipsoidal mirror E2 whose inner surfaces are mirror surfaces. A bi-ellipsoidal mirror configured to be combined so that the focal point and the common focal point are located on a straight optical axis is provided. Openings are provided at the top and bottom of the double ellipsoidal mirror, and the RM1 mirror, the RM2 mirror, and the sample holder SH for holding the specimen are inserted into the double ellipsoidal mirror through the openings. The sample holder SH can hold the sample at the position of the common focal point of the E1 and E2 mirrors, and it can be moved up and down by motor # 3 and rotated around its vertical axis by motor # 4. I can do it.

The light emitted from the light source part L is reflected by the upward mirror UM1 mirror toward the focal point of the E1 mirror perpendicular to the optical axis of the bielliptic mirror. A downward-facing RM1 mirror is installed at the focal point of the E1 mirror. The RM1 mirror can be rotated about the incident light beam by the motor # 1. In addition, a downward RM2 mirror that can be rotated by motor # 2 is installed at the focal point of the E2 mirror. The axis of rotation of RM2 mirror is parallel to the rotation axis of the RM 1 mirror. The light reflected by the RM2 mirror is reflected by the upward UM2 mirror and enters the detector section D.

By using the composite mirrors shown in FIGS. 2 and 3 as RM 1 mirrors and RM2 mirrors in twin elliptical optical device of the present embodiment, it is possible to eliminate the light that does not measure the stray twin ellipsoidal mirror outside, In addition, it enjoys the excellent features of the bi-elliptic mirror optical system (that is, light can be incident on the sample at an arbitrary incident angle, and the reflected light or transmitted light from the sample can be measured independently at an arbitrary angle). be able to.

  In the planar bielliptic optical system, the optical axis of the bielliptic mirror and the optical axis of the external optical system coincide with each other, but in the stereoscopic bielliptic optical system of this embodiment (FIG. 1), the bielliptic surface The optical axis of the mirror and the optical axis of the external optical system do not match. The light that has traveled on the optical axis of the external optical system is reflected by the upward UM1 mirror (about 45 degrees) disposed in the space below the double ellipsoidal mirror formed by the E1 mirror and the E2 mirror. It is received by the RM1 mirror facing downward (about 45 degrees) and reflected toward the E1 mirror. Thereafter, the light travels in the same way as in the case of a normal bi-elliptic mirror (FIG. 6), and the light reflected and transmitted by the sample is condensed inside the E2 mirror onto the RM2 mirror facing downward (about 45 degrees). The RM2 mirror has a structure in which a part of the collected light is reflected toward the UM2 mirror below the RM2 mirror, and at this time, the reflected light of the UM2 mirror can coincide with the original optical axis.

  In the conventional planar bielliptical optical system, the RM1 mirror and the RM2 mirror are plane mirrors. However, it is preferable to use a mushroom type mirror (FIG. 2) or a cocktail glass type mirror (FIG. 3) as the shape and structure of the RM1 mirror and RM2 mirror for this stereoscopic bi-elliptical optical system. Both the mushroom type mirror and the cocktail glass type mirror have a double structure, and a conical mirror 11 on the outer periphery and a horizontal hole 12 are formed in a part of the conical surface toward the rotational axis of the cone, A mirror 13 having an inclination of about 45 degrees is attached to the intersection, and a hole 14 is drilled upward along the rotation axis. By using the mirror 13 at the center of the cone, it is possible to transmit and receive light between the UM1 mirror and the RM1 mirror and to transmit and receive light between the RM2 mirror and the UM2 mirror. Thus, it is possible to exclude light that has not been measured, which causes stray light, to the outside of the double ellipsoidal mirror. The basic role of the mushroom mirror and the cocktail glass mirror is the same except that the direction in which light is excluded is upward or downward.

  The measurement result using a mushroom mirror is shown in FIG. The result of measuring the reflected light by making P-polarized helium neon laser light incident on the same high-purity quartz parallel plate sample as before is shown by white circles. The minimum value of the reflectance was the same as the zero signal level when no light was incident, and the reflectance was 0.0000.

  The mushroom type mirror or the cocktail glass type mirror described above reflects stray light inside the stereoscopic bi-elliptical optical system by the outer conical mirror surface and excludes it outside the bi-elliptical optical system. Even if the conical surface on the outer periphery of this mushroom mirror or cocktail glass mirror is not a mirror surface but a light absorbing surface is used to absorb stray light, it is effective in removing stray light. Further, when stray light is absorbed and removed by a member that holds the RM1 mirror and the RM2 mirror inside, the outer surface shape of the member does not necessarily need to be a conical surface, and is cylindrical, spherical, or indefinite. Also good.

  Further, as shown in FIG. 9, the method of absorbing and removing stray light by inserting a light absorbing member into the inside of the bielliptic mirror can be similarly applied to the stereoscopic bielliptic optical system shown in FIG. It is.

  Next, an embodiment of a three-dimensional ellipse optical system for the angle-dependent measurement method of the scattered light from the sample and the integrated scattered light intensity measurement method will be described. Also in this embodiment, basically, the three-dimensional elliptical optical system shown in FIG. 1 is used.

  At the common focal point F0 of the bielliptic mirror, the macro surface of the sample is arranged so as to be perpendicular to the equator plane of the bielliptic mirror and parallel to the optical axis, and the rotation angle of the RM1 mirror is appropriately selected and fixed. . The scattered light reflected by the sample proceeds not only to the E2 mirror side but also to the E1 mirror side. Scattered light traveling toward the E2 mirror is reflected by the E2 mirror and collected at the F2 focal point. The condensed light can be reflected by the RM2 mirror and returned to the original optical axis, and guided to a detector outside the E2 mirror. Here, the angle dependence of the scattered light can be measured by rotating the RM2 mirror. At this time, the RM1 mirror and the RM2 mirror can remove stray light by using the mushroom type mirror of FIG. 2 or the cocktail glass type mirror of FIG.

  Here, the same measurement was performed on two samples, an aluminum mirror having a mirror surface and a commercially available Spectralon, which is well known as a perfect diffuse reflector. FIG. 10 shows the angle-dependent measurement results of forward scattering measured with a helium neon laser (0.633 μm) as the light source, with this laser light incident almost perpendicularly on the macroscopic surface of the sample and rotating the RM2 mirror. The vertical axis in this figure is an arbitrary scale, and the aluminum mirror results are indicated by dotted lines and the Spectralon results are indicated by solid lines.

  In the aluminum mirror sample, as shown in the measurement results in FIG. 10, only the specular reflection light component is measured. Next, in the case of the Spectralon sample, since it was a very excellent diffuse reflector, the specularly reflected light component from the macro surface was not measured as shown in FIG. Only measured. However, in a sample having a general surface shape, two reflected light components can coexist. That is, a specularly reflected light component having the same incident angle and reflection angle within the same incident surface as the incident light, and a scattered light component reflected in an arbitrary direction regardless of the incident angle with respect to the macro surface of the sample. is there.

  By using the mushroom type mirror of FIG. 2 and the cocktail glass type mirror of FIG. 3 as the RM1 mirror and RM2 mirror of the stereoscopic bi-elliptical optical system, the angle dependency of the scattered light from the sample having such a general surface shape can be obtained. It can be measured.

  It is also important to separate and measure the scattered light component and the specularly reflected light component with this general surface shape sample. In this case, it is necessary to measure the angle-integrated scattered light that can measure the scattered light component to the entire space at once. As a method for realizing this measurement, the RM1 mirror uses the mushroom type mirror of FIG. 2 or the cocktail glass type mirror of FIG. 3, while the RM2 mirror uses a modified mushroom type mirror as shown in FIG. The outer periphery of the deformed mushroom type mirror is a conical mirror 21, and a horizontal hole 22 is formed in a part of the conical mirror 21 toward the rotational axis of the cone. The horizontal hole 22 is refracted inside, and a light-absorbing substance 24 is disposed behind the hole. The light that has entered the deformed mushroom-type mirror from the hole 22 is reflected by the mirror 23, reaches the light absorbing material 24, and is absorbed there.

  The shape and structure of the modified mushroom mirror is such that the specular reflection component from the sample is confined inside the mushroom mirror and completely absorbed by the light absorbing material contained therein, and the reflected light from the external conical mirror 21 is transmitted to the UM2 mirror. The apex angle of the cone is chosen to gather. By using this deformed mushroom-type mirror, the ratio of the E2 mirror surface to the total space in the scattered light component from the sample is the scattered light intensity that can be actually measured by the angular integral scattered light measurement.

  According to this angle integral scattered light measurement method, not only the above-described scattering measurement, but also (1) the angle integral measurement of light emission from the sample to the whole space, and (2) the sum of specular reflection light and transmitted light in the specular sample It is also possible to measure the spectrum.

  Finally, the stereoscopic bielliptic optical system differs from the planar bielliptic optical system in that stray light can be excluded outside the bielliptic mirror by using the conical mirror shown in FIGS. 2 and 3 together. Yes. However, in addition to this feature, when a bielliptic mirror is incorporated into an existing optical system (such as an ultraviolet / visible dispersion spectrophotometer or an infrared Fourier transform spectrophotometer), the largest inside the bielliptic mirror The structure can secure the sample space.

  This situation will be described using the above spectrophotometer as an example. Commercially available spectrophotometers have a sample chamber. By mounting various optical accessories in the sample chamber, it is possible to realize transmission measurement, reflection measurement, scattering measurement, ATR measurement, and the like. The sample chambers of many spectrophotometers have a structure in which light is collected at the midpoint of the optical axis in the sample chamber as shown in FIG. The progress of light is indicated by broken lines in the figure. In order to use the double ellipsoidal mirror in this existing spectrophotometer, the position focused by the spectrophotometer is not the midpoint on the optical axis, but the position of the RM1 mirror of the bielliptic mirror. In addition, the optical path length must be extended. In order to move the focal position in this way, several mirrors (SM1 and SM2) must be installed inside the sample chamber as shown in FIG. In the same way, since it is also focused on the RM2 mirror, several mirrors (SM3 and SM4) must be installed inside the sample chamber to return the reflected light of the RM2 mirror to the optical axis of the spectrophotometer. I must. As a result, the size of the bielliptic mirror itself entering the sample chamber of the spectrophotometer is reduced, and the sample space around the focal point F0 is also reduced.

  FIG.11 (c) is a schematic diagram when the solid elliptical optical system of this invention is installed in the sample chamber of a commercially available spectrophotometer. In the three-dimensional elliptical optical system of the present invention, the optical path length necessary for focusing on the RM1 mirror and the RM2 mirror is obtained by making the optical axis of the spectrophotometer itself and the optical axis of the bielliptic mirror three-dimensional. Secured. As a result, the double ellipsoidal mirror itself becomes large, and the sample space around the focal point F0 also becomes large.

  The present invention has been described with reference to the embodiments. However, the present invention is not limited to these embodiments, and it goes without saying that there are various modifications within the scope of the technical matters described in the claims.

The perspective view of a solid bi-elliptical optical system. Schematic diagram of a mushroom mirror for eliminating stray light. Schematic diagram of a cocktail glass-type mirror for eliminating stray light. The schematic diagram of the deformation | transformation mushroom type | mold mirror for angle integral scattered light measurement. FIG. 3 is a perspective view of a planar bielliptical optical system. Sectional view of a bielliptic mirror at the equator plane. Schematic of reflection, transmission and scattering measurement using a laser light source. The figure which shows the measurement result of the P polarization | polarized-light reflectance in the Brewster angle vicinity of a transparent quartz parallel plate sample. The figure of the light absorption member inserted in the inside of a double ellipsoidal mirror. The figure which shows the measurement result of the angle dependence of the scattered light by a sample. (A) The schematic diagram which shows the mode of the light ray (broken line in a figure) in the sample chamber of a commercially available spectrophotometer. (B) A schematic view in which a planar bi-elliptical optical system is incorporated in the sample chamber of this spectrophotometer. (C) A schematic view in which a three-dimensional bi-elliptical optical system is incorporated in a sample chamber.

Explanation of symbols

E1: Incident side ellipsoidal mirror, E2: Light receiving side ellipsoidal mirror, RM1, RM2: Downward mirror, UM1, UM2: Upward mirror, SH: Sample holder, SM1, SM2, SM3, SM4: Auxiliary mirror, L: Light source part, D: detector part, 11: conical mirror, 12: hole, 13: mirror, 14: hole, 21: conical mirror, 22: hole, 23: mirror, 24: light absorbing substance

Claims (6)

The incident-side rotational ellipsoidal mirror whose inner surface has a mirror surface, respectively and the light receiving side spheroidal mirror, the one focus and the common focus, the said common focal point and the common focal point other than the incident side spheroidal mirror 1 combined as a second focal point of focus and the light receiving side spheroidal mirror is positioned in a straight line on the optical axis, a bi-ellipsoidal mirror in which an opening portion is provided vertically,
A sample holder for holding the sample at the position of the common focus;
A first reflecting mirror for causing incident light for sample irradiation to enter the first focal point from the opening along a first axis perpendicular to the optical axis;
A second reflector disposed at the first focus and rotatable about the first axis;
A third reflector disposed at the second focal point and rotatable about a second axis parallel to the first axis;
A fourth reflecting mirror that reflects the light reflected by the third reflecting mirror toward the detector;
Before Stories second reflecting mirror has a first surface for entering the incident light reflected by the reflecting mirror to the common focal point is reflected by the inner surface of the incident-side rotary ellipsoidal mirror, said other incident light twin and a surface for reflecting the outside of the ellipsoidal mirror, the third reflecting mirror, the measurement light reflected by the inner surface of the light receiving side spheroidal mirror After interacting with the sample to the fourth reflecting mirror A solid bielliptic optical device comprising a surface to be incident and a surface that reflects light other than measurement light to the outside of the bielliptic mirror. In the three-dimensional bi-elliptic type optical device according to claim 1, wherein at least a portion and / or the light receiving side spheroidal opposite space to the side where the incident light exists for the incident-side rotary ellipsoidal mirror inside the optical axis A three-dimensional elliptical type comprising a light absorbing member functioning as means for reducing stray light inserted into at least a part of a space opposite to the side where measurement light exists with respect to the optical axis inside the surface mirror Optical device.   2. The three-dimensional ellipsoidal optical device according to claim 1, wherein the second reflecting mirror and / or the third reflecting mirror are disposed inside a conical member connected to a rotating shaft, and the conical member has an outer surface as a mirror surface. And a hole extending from the apex to the reflecting mirror disposed inside, and a hole extending from the conical side surface to the reflecting mirror disposed inside.   2. The three-dimensional ellipsoidal optical device according to claim 1, wherein the second reflecting mirror and / or the third reflecting mirror are disposed inside a conical member connected to a rotating shaft, and the conical member has an outer surface as a mirror surface. And a hole extending from the bottom surface to the reflecting mirror disposed inside, and a hole extending from the conical side surface to the reflecting mirror disposed inside.   2. The three-dimensional ellipsoidal optical device according to claim 1, wherein the second reflecting mirror and / or the third reflecting mirror are arranged inside a member connected to a rotation shaft, and the outer surface of the member is a light absorbing surface. And a hole extending in parallel to the rotation axis from the internal reflector to the side surface of the member and a hole extending perpendicularly to the rotation axis from the internal reflection mirror to the side surface of the member.   2. The three-dimensional ellipsoidal optical device according to claim 1, wherein the third reflecting mirror includes a conical member connected to a rotation shaft, and the conical member has a mirror surface on the outer surface, and a specular reflection component from the sample. A three-dimensional bi-elliptical optical device characterized by having a hole on the side surface that absorbs the incident light.

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